1. Field of Invention
This invention relates to modular networks in general and in particular to high capacity modular networks.
2. Related Art
The exponential growth in available fiber transmission capacity is due to periodic large jumps in bit rates in the past, and the availability of higher densities of wavelength division multiplexing (WDM) more recently. The growth in number of subscribers, time spent on line, and types of interaction, contribute to a steady and rapid growth of traffic demand.
WDM, dense WDM (DWDM), and optical switching become more and more available. Presently, the terminal capabilities are not a limiting factor in bandwidth use. Conversely, the servers are a limiting factor for network growth but this appears to be more a cost issue than a technical limitation. In multi-node networks the traffic interconnectivity is engineered according to the observed or presumed traffic demand and the available infrastructure (transport) like point-to-point fiber and fiber rings. For increasing the network capacity, the existing switches may be expanded up to their maximal capacity, additional switches may be added, or the existing switches may be replaced with larger models.
A solution for collecting more traffic in a local area network (LAN) is to use multiple parallel SONET rings. However, this solution has to address the problem of balancing the traffic and the problem of fixed assignment of traffic sources to transport rings.
Other solutions to increase the capacity of the network may include replacing the existing switches with larger capacities switches, rather than using an increased number of switches at a node. This requires in most cases, switches with a capacity beyond the available switch capacity.
For increasing the capacity of an existing network, the link capacity can be increased by providing more wavelengths on more optical fibers. As a result, the equipment at the nodes must allow incremental equipment growth, in other words to be scalable. Changes in the network topology such as adding new backbone sites, or another direct route between two previously unconnected backbone nodes also require that the backbone, or core nodes to be scalable. The deployment of a new backbone node at a new site is a major challenge which is generally circumvented by upgrading the existing network.
Accordingly, there is a need for a scalable network architecture that allows both backbone nodes and network capacity to increase in a manner that avoids cost increases and lower efficiencies that would result from increasing network capacity by reshaping a conventional network topology by adding switches and more hops.